#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
int main()
{
	double sum=0;
	int i = 0, flag = 1;
	for (i = 1; i <= 100; i++)
	{
		sum = sum + flag*(1.0/i);
		flag = -flag;
	}
	printf("%lf\n", sum);
	return 0;
}